This invention relates to circuits for controlled charging and discharging of energy storage devices such as capacitors associated with a load, and more particularly to a new and improved circuit for preventing adverse conditions such as short circuits associated with the load from affecting the supply from which the capacitors are charged as well as the circuits associated with that supply.
One area of use of the present invention is in controlled firing of electro-explosive devices, although the principles of the invention can be variously applied. Electro-explosive devices find use in a variety of applications, for example parachute canopy release mechanisms, pressurized gas release devices for inflating floatation equipment such as life vests or life rafts, and many other applications. A typical circuit for activating an electro-explosive device includes a capacitor which is charged from a supply and then discharged in a controlled manner through the device. These electro-explosive devices or actuators normally have metal bodies which contain the explosive charge, and the explosive ignition bridgewire normally is insulated from the metal body of the device. In many instances, these metal-cased electro-explosive devices are attached to the metal body of the apparatus in which they operate and then the same metal body is used as the common electrical return line or path for the electrical system of the apparatus. Thus, a short circuit condition between the normally insulated ignition bridgewire and metal case of the electro-explosive device can have a detrimental effect on the apparatus electrical system. It would, therefore, be highly desirable to provide a capacitor charging and discharging control and firing circuit for an electro-explosive device which avoids or prevents such effects on the electrical system of which the device is a part.